OK, I still don't have an answer from my own experience, but some googling produced a lot of lists and articles indicating that BOTH Lilium and Hemerocallis (daylilies) are seriously toxic to cats, causing severe kidney damage. Looks like daylilies aren't similarly toxic to dogs or bunnies. (or groundhogs, from my own observation)
Regardless, I'm glad you chose the "better safe than sorry" approach and got your cat treated.
